In　this　research,　we　report　the　use　of　a　commercial　epoxy　based　nanocomposite　with　2　wt　%　nanosilica　to　enhance　the　fracture　toughness　and　wear　performance　of　neat　epoxy　under　marine　environment.　The　mechanical　behaviours　of　neat　epoxy　and　the　nanosilica　enhanced　epoxy　composite　are　characterised　after　different　periods　of　immersion　in　sea　water　(0　day,　7　days　and　30　days).　The　experimental　results　indicate　that　sea　water　immersion　does　not　greatly　affect　the　tensile　behaviours　of　the　epoxy　or　the　nanosilica　enhanced　epoxy　nanocomposite.　However,　the　fracture　toughness　of　the　neat　epoxy　is　weakened　by　the　sea　water　immersion　with　an　18.5%　decrease　after　7　days　immersion　and　no　further　decrease　after　30　days　immersion.　The　fracture　toughness　of　the　nanocomposite　also　decreases　after　immersion,　but　the　final　value　after　immersion　is　comparable　to　that　of　the　neat　epoxy　without　immersion.　The　friction　coefficient　of　the　neat　epoxy　increases　but　that　of　the　nanocomposite　decreases　with　increasing　immersion　in　sea　water.　The　proposed　mechanisms　are　also　discussed　here.　(C)　2016　Elsevier　B.V.　All　rights　reserved.